$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
10.19
\begin{equation} \begin{gathered}\label{equation:monomorphism-of-Cech-nerves} \xymatrix@C =50pt@R=50pt{ & Y \ar [dr]^{g} & \\ X \ar [ur]^{f} \ar [rr]^{h} & & Z, } \end{gathered} \end{equation}